1. Field of the Invention
This invention relates to blow molded plastic containers, and particularly those containers having an upper dome or bell portion that is designed to be gripped by a consumer during use.
2. Description of the Related Technology
Many products that were previously packaged using glass containers are now being supplied in plastic containers, such as containers that are fabricated from polyesters such as polyethylene terephthalate (PET).
PET containers are typically manufactured using the stretch blow molding process. This involves the use of a preform that is injection molded into a shape that facilitates distribution of the plastic material within the preform into the desired final shape of the container. The preform is first heated and then is longitudinally stretched and subsequently inflated within a mold cavity so that it assumes the desired final shape of the container. As the preform is inflated, it takes on the shape of the mold cavity. The polymer solidifies upon contacting the cooler surface of the mold, and the finished hollow container is subsequently ejected from the mold.
The use of blow molded plastic containers for the purpose of packaging liquids that are processed by the hot fill and/or pasteurization processes has been known for some time. The hot fill process involves filling the containers while the liquid product is at an elevated temperature, typically 68° C. to 96° C. (155° F.-205° F.) and usually about 85° C. (185° F.) in order to sterilize the container at the time of filling. Containers that are designed to withstand the hot fill process are known as “hot fill” or “heat set” containers. Such containers are typically designed with sidewalls that include one or more recessed vacuum panels that are designed to flex due to the temperature changes and consequent volumetric expansion and contraction that takes place during processing. In many instances, the recessed vacuum panels also provide convenient handholds that facilitate gripping of the container by consumers.
One type of conventional container design includes a lower portion that is shaped to receive a label and an upper dome or bell portion that is separated from the lower label portion by a waist. In some instances, the dome is constructed to extend outwardly from a longitudinal axis of the container to a greater extent than the label portion so that container to container contact during filling and packaging will occur between the respective dome portions, protecting the label portions against flexure that could cause delamination of the label. This is known in the industry as label protection.
The label portion may be constructed to flex inwardly during the hot fill process in a controlled fashion to adjust for volumetric changes within the container. However creasing or other significant shape changes are undesirable because of the need to provide label support. The waist of the container structurally isolates the dome portion from the label portion so that flexure in one will not be transmitted to the other. It also provides reinforcement against flexure of both the dome portion and the label portion. The amount of reinforcement provided to the label portion and the dome portion by the waist in conventional designs has tended to be about same. However, in some instances it would be desirable to provide more reinforcement to the label portion. One reason for this is that in the past, it has been found to be difficult as a matter of design to provide effective gripping recesses within a dome or bell portion while maintaining material costs at an economically acceptable level, because the force created by a consumer while gripping the container has the tendency to collapse portions of the dome or bell portion. In addition, containers of this type may experience damage such as creasing as a result of container-to-container contact on the filling line.
A need exists for an improved plastic container having an upper dome or bell portion that is designed to be gripped by a consumer during use, which provides improved optimization of structural stability and material costs with respect to conventional designs.